@article{ZNSL_1984_137_a4,
     author = {V. P. Orevkov},
     title = {Upper bounds for lengthening of proofs after cut-elimination},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {87--98},
     year = {1984},
     volume = {137},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1984_137_a4/}
}